Natural Gas Engine-Driven Air Compressors
In a typical direct-drive rotary screw air compressor, ambient air enters through a filter on what is called the air end of the compressor. The compressor is driven by a prime mover and is filled with oil for smooth operation. The air and oil mixture flows into and is compressed by a rotary screw assembly. After compression the air and oil mixture flows through a separator tank to separate the oil from the air. The oil, which collects at the bottom of the separator tank, flows through an oil cooler and back to the air end after being filtered. The compressed air leaves the separator tank and is reduced in temperature by an aftercooler. Finally, water in the air is removed by a moisture separator before the air enters the industrial plant air system.
Using a natural gas engine instead of an electric motor is a particularly good fit with rotary screw compressors widely used in industrial plants. Rotary screw compressors are positive displacement devices which are usually driven at constant speed by an electric motor and use compressor inlet throttling if required to operate at part load.Compressor efficiency can be much higher at part load with a natural gas engine drive than with an electric motor drive because the speed of the engine can be reduced to track air demand.